This invention relates in general to methods of fabrication of cylindrical devices comprising flexible tube or belt supported on a rigid cylindrical support member and the product of such fabrication method.
Coated cylinders are employed extensively in various arts. For example coated cylinders may be utilized as electrostatographic imaging members, drive rolls, calendaring rolls, fuser rolls, transport rolls, and the like. Similarly, flexible tubes or belts are commonly utilized for numerous purposes such as electrostatographic imaging members, conveyor belts, drive belts and the like.
Flexible electrostatographic imaging members, e.g. belts, are well known in the art. Typical electrostatographic flexible imaging members include, for example, photoreceptors for electrophotographic imaging systems, and electroreceptors or ionographic imaging members for electrographic imaging systems. Both electrophotographic and ionographic imaging members are commonly utilized in either a belt or a drum configuration. These electrostatographic imaging member belts may be seamless or seamed. For electrophotographic applications, the imaging members preferably have a belt configuration. These belts often comprise a flexible supporting substrate coated with one or more layers of photoconductive material. The substrates may be inorganic such as electroformed nickel or organic such as a film forming polymer. The photoconductive coatings applied to these belts may be inorganic such as selenium or selenium alloys or organic. The organic photoconductive layers may comprise, for example, single binder layers in which photoconductive particles are dispersed in a film forming binder or multilayers comprising, for example, a charge generating layer and a charge transport layer.
Electrophotographic imaging members having a belt configuration are normally entrained around and supported by at least two rollers. Generally, one of the rollers is driven by a motor to transport the belt around the rollers during electrophotographic imaging cycles. Since electrophotographic imaging belts, particularly welded seam belts, are not perfectly cylindrical and, more specifically, tend to be slightly cone shaped, these flexible belts tend to "walk" axially along the support rollers. Belt walking causes one edge of the belt to strike one or more edge guides positioned adjacent the ends of the rollers to limit axial movement. Friction between the edge guide and the edge of the photoreceptor belt can cause the belt to wear, rip, buckle and otherwise damage the belt.
Belts driven around supporting rollers can slip relative to the surface of the roller during stop and go operations. Belt slipping has been a serious problem when the surface contact friction between the backside of the imaging belt and the elastomeric outer surface of the drive roll is substantially reduced as a result of aging of the elastomeric material or deposition and accumulation of undesirable foreign material on the surface of the drive roll. This slippage can adversely affect registration of images, particularly where multiple, sequentially formed and transferred images must be precisely registered with each other in demanding applications such as color imaging. Further, where welded belt seams encounter slippage, sophisticated detection systems are required to ensure that images are not formed on the seam when the seam shifts due to slippage. Also, there are other serious drawbacks in terms of belt tracking and problems with good image registration. Welded belts, because of the difficulties associated with perfectly aligning overlapping ends during seam welding, are not as concentric as desired.
Often, the supporting rollers for an electrophotographic imaging belt have relatively small diameters. Constant flexing of the belt around small diameter support rollers can cause the seam to crack. The cracks propagate and cause belt delamination because of the flexing as well as fatigue. In addition to these seam cracking and delamination problems, dynamic flexing of the belt around the small diameter support rollers also causes cracking of the outer imaging layer. Cracking of the outer imaging layer leads to copy print defects.
The region of a belt located between supporting rollers can vibrate and undesirably alter the often critical distances between the belt imaging surface and devices such as optical exposure means, charging corotrons, development applicators, transfer stations and the like.
In addition, the anti-curl back coating on a belt tends to wear during cycling and such wear reduces the effectiveness of the anti-curl back coating from preventing curling of the edges of the belt. Curling of the belt also adversely affects the critical distances between the belt imaging surface and adjacent processing stations.
Another type of electrophotographic imaging members that is well known in the art are drum type photoreceptors. Some photoreceptors are coated with one or more coatings. Coatings may be applied by well known techniques such as dip coating or spray coating. Dip coating of drums usually involves immersing of a cylindrical drum while the axis of the drum is maintained in a vertical alignment during the entire coating and subsequent drying operation. Because of the vertical alignment of the drum axis during the coating operation, the applied coatings tend to be thicker at the lower end of the drum relative to the upper end of the drum due to the influence of gravity on the flow of the coating material. Coatings applied by spray coating can also be uneven, e.g., orange peel effect. Coatings that have an uneven thickness do not have uniform electrical properties at different locations of the coating. Also, the coating of drums in a batch operation is time consuming and costly. In addition, the many handling steps required for batch drum coating processes tend to increase the likelihood that one or more coatings will be damaged or contaminated. Moreover, dip or spray coated photoreceptor drums do not exhibit the superior electrophotographic characteristics of flexible electrostatographic imaging belts. Moreover, the coatings are difficult to remove without damaging the underlying drum during reclaiming operations thereby rendering the drum unsuitable for recycling.
Similar difficulties have been experienced with fabrication of other types of coated drums such as coated fuser rolls and sheet transport rolls.